System and apparatus for patterned media with reduced magnetic trench material

ABSTRACT

A bit patterned magnetic media design for reducing the amount of magnetic material located in the trenches between topographic features is disclosed. An intermediate non-magnetic layer is deposited on the topography prior to depositing the functional magnetic layer on the topographic substrate features. The non-magnetic layer increases the width of the land regions that will ultimately support the functional magnetic layer. The non-magnetic layer also reduces the amount of trench deposition that can occur in the subsequent deposition of the magnetic recording layer. By eliminating most of the magnetic trench material, the amount of magnetic flux and readback interference produced by the trench material is reduced to an acceptable level.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates in general to patterning magnetic mediafor hard disk drives and, in particular, to an improved system, methodand apparatus for hard disk drive patterned magnetic media having areduced amount of magnetic trench material.

2. Description of the Related Art

Data access and storage systems generally comprise one or more storagedevices that store data on magnetic storage media. For example, amagnetic storage device or hard disk drive (HDD) includes one or moredisks and a disk controller to manage operations concerning the disks.The hard disks themselves are usually fabricated from an aluminum alloy,glass or a mixture of glass and ceramic, and are covered with a magneticmedia coating that contains the bit pattern.

One common approach to making the bit patterned media (BPM) or discretetrack media (DTM) on the disks is to create topographic patterns on thesubstrate, followed by blanket deposition of the magnetic recordinglayers. Magnetic material deposited on the tops (or “lands”) oftopographic features is used for recording, while material deposited inthe etched relief areas (or “trenches”) is not intended to be used forrecording.

However, it has been shown through both modeling and experiments thatmagnetic material located in the trenches produces significant unwantedmagnetic flux, which interferes with the readback signal. The presentinvention seeks to reduce the amount of magnetic material ending up inthe trenches and thereby to reduce readback interference caused by thetrench material.

Referring to FIG. 1, a schematic sectional side view of a disk 11 havingconventional patterned media formed on a substrate 13 is shown. Themedia includes a soft underlayer 15, an exchange break layer 17 andnon-magnetic pillars 19 or raised track structures having trenches 25therebetween. A magnetic layer is blanket deposited on thetopographically patterned substrate. This deposition forms a magneticrecording layer 21 (i.e., formed as “islands”) on the pillars 19, andsome magnetic material 23 in the trenches 25 between the pillars 19. Themagnetic material 21 deposited on top of the pillars 19 is used forrecording, while the trench material 23 generates unwanted magnetic fluxthat increases the background noise level and interferes with readbackoperations of the disk drive.

The amount of magnetic material in the trenches can be reduced bydepositing the magnetic material at an angle with respect to normalincidence. However, angled deposition does not completely eliminate thetrench material due to the complex, three-dimensional shapes of thepillars (particularly for BPM), and the fact that sputter deposition hasonly limited directionality. Furthermore, angled deposition can resultin significant deposits on the sidewalls of the topography, which alsohas unintended effects on the magnetic properties of the islands ortracks.

An alternative solution to this problem is to “poison” the trenchmaterial. Poisoning the trench material is attractive from the point ofview of totally eliminating the magnetism of the trench material.However, there are some challenges to successfully implementing such anapproach for small feature sizes, including the effects of dimensionaldistortion of feature shapes due to diffusion processes. Thus, animproved solution for reducing the unwanted effects of having magneticmedia located in the trenches between the topographic features of diskswould be desirable.

SUMMARY OF THE INVENTION

Embodiments of a system, method and apparatus for reducing the amount ofmagnetic material located in the trenches between topographic featuresin bit patterned media are shown. The invention reduces or eliminatesthe readback interference caused by the trench material. Although theinvention described herein may leave a small amount of magnetic materialin the trenches, no diffusion is used. Therefore the negativeconsequences of diffusion are eliminated when scaling down the islandsize to densities beyond what is currently achieved in conventionalperpendicular recording demonstrations.

In one embodiment, an intermediate and significantly thickernon-magnetic layer is deposited on the topography prior to depositingthe functional magnetic layer on the topographic substrate features.Thin seed layers, underlayer structures and/or adhesion layers may bedeposited directly beneath the magnetic layer, either above or below theintermediate layer. The non-magnetic layer has the effect of increasingthe lateral diameter of the land regions that will ultimately supportthe functional magnetic layer. This also increases the effective areafilling factor of magnetic material that contributes to the readbacksignal. In addition, the non-magnetic layer reduces the amount of trenchdeposition that can occur in the subsequent deposition of the magneticrecording layer. By eliminating most of the magnetic trench material,the amount of magnetic flux and readback interference produced by thetrench material is reduced to an acceptable level.

Even if the non-magnetic material is incidentally deposited on the sidewalls, it will not cause any undesired effects, such as thoseexperienced with magnetic materials. Overall the degree of sidewallovergrowth effects can be mitigated by varying the deposition angle withrespect to the surface normal of the substrate.

The magnetic properties of the recording layers are fairly independentof the non-magnetic interlayer thickness. For example, TaPd alloys orTa/Pd bilayers may be used for the non-magnetic layer to fulfill thisrequirement.

The foregoing and other objects and advantages of the present inventionwill be apparent to those skilled in the art, in view of the followingdetailed description of the present invention, taken in conjunction withthe appended claims and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features and advantages of the presentinvention are attained and can be understood in more detail, a moredetailed description of the invention may be had by reference to theembodiments that are illustrated in the appended drawings. However, thedrawings illustrate only some embodiments of the invention and thereforeare not to be considered limiting of its scope as the invention mayadmit to other equally effective embodiments.

FIG. 1 is a schematic sectional side view of conventional patternedmedia for a magnetic media disk;

FIG. 2 is a schematic sectional side view of one embodiment of asub-assembly of patterned media for a magnetic media disk beforedeposition of the magnetic layer, and is constructed in accordance withthe invention;

FIG. 3 is a schematic sectional side view of one embodiment of thepatterned media of FIG. 2 after deposition of a magnetic recording layerand is constructed in accordance with the invention;

FIG. 4 depicts plots of Micro-Kerr remnant reversal curves for differentnon-magnetic interlayer thicknesses on patterned media constructed inaccordance with the invention; and

FIG. 5 is a schematic diagram of one embodiment of a disk driveconstructed in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 2-5, embodiments of a system, method and apparatusfor reducing the amount of magnetic material located in the trenchesbetween topographic features in bit patterned media are shown.

In one embodiment (FIG. 2), the invention comprises a magnetic mediadisk 31 for a hard disk drive. The disk may include a substrate 33, asoft underlayer 35 on the substrate 33, and an optional exchange breaklayer 37 on the soft underlayer 35. Topographic formations or islands 39extend from the substrate 33 and/or layers formed thereon. Anintermediate non-magnetic material 41 is deposited on this structure 39,followed by the deposition of a magnetic recording layer 43 (FIG. 3).FIG. 2 schematically illustrates the structure after depositing theintermediate layer 41. FIG. 3 schematically shows the media structureafter deposition of the magnetic recording layer 43. This process andconfiguration reduces the amount of magnetic material deposited in thetrenches 45.

The non-magnetic material is deposited under conditions that result inlateral (i.e., left and right in FIGS. 2 and 3) as well as verticalgrowth of the film. Material extends outward laterally from the tops ofthe islands 39, which narrows the access aperture for approachingmaterial from any subsequent further deposition of material. Theseself-shadowing effects prevent a fast coalescence of adjacentislands/pillars and thus prevent any undesired coupling between adjacentislands/pillars. Using an angle of incidence 47 (FIG. 3) other thannormal promotes lateral growth of the film and side wall growth, thusincreasing the island width and the effective area contributing to thereadback signal.

The magnetic properties of the recording layers are fairly independentof the non-magnetic interlayer thickness. For example, materials such asTa and Pd may be used to fulfill this requirement as demonstrated in theMicro-Kerr measurements in FIG. 4. FIG. 4 is a plot of Micro-Kerrremnant reversal curves 51, 53, 55 for different non-magneticinterlayers for a Co/Pd multilayer media. In this example the islandsare 50 nm in width and formed at a 100 nm pitch. The island switchingfield is similar in all three cases (i.e., about 11 kOe). However, foran interlayer having a thickness of 28.5 nm, a small shift is observedto lower the reversal fields. The Kerr signal from the trench reversal(at about 2-3 kOe) is reduced with increasing interlayer thickness,which indicates that there is less magnetic trench material for thickerinterlayers. Overall, the thickness of the non-magnetic layer should betuned depending on the lateral periodicity of the pattern and theinitial trench width of the pre-patterned substrate. This maximizes theeffective area that contributes to the readback signal without causingany inter-island exchange coupling.

Since access to the trenches is reduced by deposition of theintermediate layer, significantly less magnetic material is deposited inthe trenches as also confirmed experimentally by the Kerr measurementsin FIG. 4. The growth of the intermediate layer effectively “pinchesoff” the access route for deposition of further material in thetrenches. Choosing to deposit the magnetic material at an angle otherthan normal can further reduce deposition of magnetic trench material.Based on experimental results, reducing the amount of trench material bya factor of two or three may be sufficient to achieve adequate readbacksignal to noise ratio.

Using magnetic multilayers as magnetic media, one may use differentangles for two multilayer materials, which leads to proper multilayerstructures on top of the islands. Predominantly, only one materialreaches the trenches (i.e., with normal incidence) and the othermaterial reaches the sidewalls (i.e., at an angled incidence). Thus,different material compositions are formed on the sidewalls and trencheswhich may result in non-magnetic phases in the trenches as well as onthe sidewalls.

In addition, subsequent oxidation processes may play a significant rolein such configurations. For example, a Pd/Co multilayer may be used withPd deposited normal to the substrate surface and Co deposited at anangle. This results in a Pd-rich trench phase (non-magnetic) and aCo-rich side wall phase. However, the Co on the sidewalls does not forma continuous film and thus oxidizes to non-ferromagnetic Co-oxideclusters after the media is exposed to ambient air. In contrast, themultilayer on top of the islands are protected by a final cap layer,such as a Pd cap having a thickness of 2 nm.

As shown in the drawings, deposition of the intermediate layer causesthe lateral dimensions of the lands or islands to grow. Such lateralgrowth (and additional curvature, which may develop when depositing theinterlayer) needs to be taken into account in the magnetic design of themedia from a recording system point of view. For example, larger landsor islands increase overall readback flux, which is desirable, but alsoincreases dipole interactions between islands in BPM, which mayadversely affect switching field distribution. See, e.g., thepublication, Separating Dipolar Broadening from the Intrinsic SwitchingField Distribution in Perpendicular Patterned Media, O. Hellwig, et al,Appl. Phys. Lett. 90, 162516 (2007). Such effects may need to becountered by reducing the moment or thickness of the magnetic recordinglayer. For DTM, increased land width may affect the optimal choice forhead element widths and off-track and adjacent track erasure effects.

In one embodiment, the invention comprises a magnetic media diskincluding a substrate, a plurality of topographic features formed on thesubstrate and defining trenches therebetween, a layer of non-magneticmaterial formed on the topographic features and on the trenches, and alayer of magnetic material formed on the layer of non-magnetic materialon at least the topographic features to define a recording layer.

Referring again to the embodiment of FIGS. 2 and 3, the layer ofnon-magnetic material is segmented into portions 41 that are located onthe topographic features 39, and portions 67 that are located in thetrenches 45. In addition, the layer of magnetic material is segmentedinto magnetic portions 43 on non-magnetic portions 41, and magneticportions 65 on non-magnetic portions 67. Each of the non-magneticportions 41 has a width 61 that is greater than a width 63 of thetopographic features 39, but narrower than a width 69 of the magneticportions 43. However, the widths of non-magnetic portions 67 are greaterthan the widths of magnetic portions 65.

In other embodiments, the topographic features are non-magnetic, andhave sidewalls on which some of the non-magnetic material is located. Atleast portions of the layer of magnetic material also are located on thenon-magnetic material formed on the trenches. The substrate has asurface that defines a planar direction, the topographic features extendin a direction that is normal to the planar direction, and the layer ofnon-magnetic material located on the topographic features extendssubstantially parallel to the planar direction.

In still another embodiment, a soft underlayer formed on the substrate,an optional exchange break layer formed on the soft underlayer, and thetopographic features extend from the exchange break layer such that thetrenches also are located on the exchange break layer. The non-magneticlayer may have a thickness of approximately 15 to 30 nm (e.g., 15 to 20nm in one embodiment), depending on the pattern periodicity. Inaddition, the non-magnetic layer may comprise a TaPd alloy or Ta/Pdbilayers. The disk may comprise thin seed layers, underlayer structuresand/or adhesion layers deposited directly beneath the magnetic layer,either above or below the intermediate layer.

As shown and described herein, the topographic features may compriseislands having a spacing therebetween. The non-magnetic materialsegments located on the islands have a smaller spacing between them thanthe spacing between the islands. In another embodiment, an aperture isdefined between adjacent islands, one trench is defined in eachaperture, and the non-magnetic material reduces the size of eachaperture.

Referring now to FIG. 5, a schematic drawing of one embodiment of aninformation storage system comprising a magnetic hard disk file or drive111 for a computer system is shown. Drive 111 has an outer housing orbase 113 containing at least one magnetic disk 115. Disk 115 is rotatedby a spindle motor assembly having a central drive hub 117. An actuator121 comprises one or more parallel actuator arms 125 in the form of acomb that is pivotally mounted to base 113 about a pivot assembly 123. Acontroller 119 is also mounted to base 113 for selectively moving thecomb of arms 125 relative to disk 115.

In the embodiment shown, each arm 125 has extending from it at least onecantilevered load beam and suspension 127. A magnetic read/writetransducer or head is mounted on a slider 129 and secured to a flexurethat is flexibly mounted to each suspension 127. The read/write headsmagnetically read data from and/or magnetically write data to disk 115.The level of integration called the head gimbal assembly is the head andthe slider 129, which are mounted on suspension 127. The slider 129 isusually bonded to the end of suspension 127. The head is typicallyformed from ceramic or intermetallic materials and is pre-loaded againstthe surface of disk 115 by suspension 127.

Suspensions 127 have a spring-like quality which biases or urges the airbearing surface of the slider 129 against the disk 115 to enable thecreation of the air bearing film between the slider 129 and disksurface. A voice coil 133 housed within a voice coil motor magnetassembly 134 is also mounted to arms 125 opposite the head gimbalassemblies. Movement of the actuator 121 (indicated by arrow 135) bycontroller 119 moves the head gimbal assemblies radially across trackson the disk 115 until the heads settle on their respective targettracks.

While the invention has been shown or described in only some of itsforms, it should be apparent to those skilled in the art that it is notso limited, but is susceptible to various changes without departing fromthe scope of the invention. For example, the invention also is suitablefor magnetic media applications such as magnetic tape.

What is claimed is:
 1. A hard disk drive, comprising: an enclosurehaving a magnetic media disk rotatably mounted thereto and an actuatorhaving a head for reading data from and writing data to the magneticmedia disk; the magnetic media disk further comprising: a substrate; aplurality of topographic features formed on the substrate and definingtrenches therebetween; a layer of non-magnetic material formed on thetopographic features; a layer of magnetic material formed on the layerof non-magnetic material on at least the topographic features to definea recording layer; the layer of non-magnetic material is segmented intoportions that are located on respective ones of the topographicfeatures, and each of the portions has a width that is greater than awidth of said respective ones of the topographic features; and the layerof magnetic material is segmented into portions that are located onrespective ones of the portions of the non-magnetic material, and eachof the portions of the magnetic material has a width that is greaterthan the width of said respective ones of the portions of thenon-magnetic material.
 2. A hard disk drive according to claim 1,wherein the topographic features are non-magnetic and have sidewalls onwhich some of the non-magnetic material is located; at least portions ofthe layer of magnetic material are also located on non-magnetic materialformed on the trenches; and the magnetic material in the trenches isoxidized to a non-ferromagnetic material, and the magnetic material onthe topographic features is protected by a cap layer to retain magneticproperties.
 3. A hard disk drive according to claim 1, wherein thesubstrate has a surface that defines a planar direction, the topographicfeatures extend in a direction that is normal to the planar direction,and the layer of non-magnetic material located on the topographicfeatures extends substantially parallel to the planar direction; andfurther comprising a soft underlayer formed on the substrate, anexchange break layer formed on the soft underlayer, and the topographicfeatures extend from the exchange break layer such that the trenchesalso are located on the exchange break layer.
 4. A hard disk driveaccording to claim 1, further comprising at least one additional layerselected from the group consisting of a seed layer, an underlayerstructure and an adhesion layer, said at least one additional layerbeing deposited directly beneath the magnetic layer, and said at leastone additional layer being located above or below the non-magneticlayer.
 5. A hard disk drive according to claim 1, wherein thetopographic features comprise islands having a spacing therebetween, andthe non-magnetic material located on the islands have a smaller spacingtherebetween than the spacing between the islands.
 6. A hard disk driveaccording to claim 1, wherein an aperture is defined between adjacentones of the topographic features, one trench is defined in eachaperture, and the non-magnetic material reduces a size of each aperture.